High-frequency transformer



NOV. 6, 1928. 1,690,228

R. A. HEISING HIGH FREQUENCY TRANSFORMER Original Filed Dec. :51, 1925Fig.2. /0 /L[Ew l /2 9 ifiw ffiw 2/ if E? WI w -a 'l-l-l +l lnvenTor:Raymond A.Heism7 Patented Nov. 6, 1928 UNITED STATES PATENT "OFF-ICE.

RAYMOND A. HEISING, OF MILLBURN, NEW JERSEY, ASSIGNOR TO WESTERN ELEC-TRIC'GOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEWYORK.

HIGH-FREQUENCY TRANSFORMER.

Original application flied December 81, 1928, Serial No. 683,629.Divided and this application filed August 20, 1925.

This invention relates to radio signaling systems and more particularlyto a transformer for coupling high frequency circuits.

This application is a division of an appli- 6 cation of R. A. Heising,Serial No. 683,629, filed December 31, 1923.

In radio receiving circuits employing high frequency amplification it isdesirable to intercouple the amplifying devices by means of 10 circuitstuned to the incoming signal waves.

Thus the coupled circuit between the ampl fiers and between the highfrequency amplifiers and the detector should be selectlve of thefrequency of the signal waves received by the antenna. The input andoutput circuits of the amplifiers being both tuned to the samefrequency, considerable difficulty has been encountered due to theproduction of undesired oscillations or singing in the amplifiercircuits. This singing is largely due to a coupling effect between theinput and output circuits of the amplifier.

The usual method for preventing singing in amplifier circuits is toinclude a resistance at some point in the coupled circuits or else toconstruct the primary winding of the transformersof resistance wire. Inaccordance with this invention a transformer, prov1ded with adjustablemeans for controlhng the electrical characteristics ofits primary andsecondary circuits, is used to intercouple the high frequency amplifiersandto couple the amplifiers to a detector.

It is an object of this invention to provide for intercoupling highfrequency circuits in such manner that singing 1s prevented.

A feature of the invention is an adjustable high frequency transformer.

The above object and others, which will be 40 apparent as the nature ofthe invention is disclosed, are accomplished by employing ar. air coretransformer having primary and secondary windings. Effective resistanceis 1ntroduced by the hysteresis effect of a. magnetic ribbon adjustablyassociated with the primary winding. The effective inductance of thesecondary winding is varied by means of a conductive core adj ustablyassociated therewith. V

I0 Althou h the novel features which are believed to e characteristic ofthis invention will be pointed out with particularity in the Serial No.51,305.

claims appended hereto, the invention itself, its ob ects andadvantages, the manner of itspart thereof in which Fig. 1 shows anadjustable high frequency transformer constructed in accordance withthis invention, and Fig. 2 shows a circuit arrangement in which thistransformer may be used.

The coupling transformer shown in detail in Fig. 1 comprises an air coretransformer having primary and secondary windings l and 2, respectivelywound on an insulating core 3 secured to a supporting frame 4. Thesupporting frame is shown as of insulating material and may be of anymaterial and-of any form. Arms 5 of frame 4 are adapted to supportelements 6 and 7 axially of the core 3. Windings 1 and 2, when used withdischarge devices as herein described, are each wound to cooperate withthe internal capacity of the associated discharge device to constitute atuned circuit. When used with other forms of high impedance amplifiersand detectors, such windings should be designed to have the necessaryinductance and distributed capacity to determine its tuning. The element6 consists of the spirally Wound laminated strip or ribbon with itsconvolutions spaced apart. This element is carried by a threaded shankengaging a screw threaded opening in one of the arms 5 and is associatedwith the primary winding 1.

A conductive element 7, which may be a copper or brass rod, is providedwith a screw thread to engage a screw threaded opening in the other arm5. The area of the rod 7 should be as large as possible. and preferablyits diameter should be only slightly less than the internal diameter ofthe secondary winding 2. The transformer should preferably be mounted sothat the only coupling between the windings 1 and 2 is that due to theirmutual inductance. In other words, the supporting means for the windingsshould in troduce substantially no coupling effect between the primaryand secondary circuits of the transformer.

High frequency current flowing through primary winding 1 will produce amagiietic field in the space surrounding it. With the element 6 lying inthis magnetic field losses will be introduced into the primary circuitdue to edd currents traversing the ribbon winding an the hysteresis ofthe iron. These losses appear as an effective resistance load in theprimary circuit. Because of the high frequencies involved the item doesnot function to decrease the reluctance of the magnetic circuit. Hencethe reactance of the rimary circuit and the mutual inductance etween thetransformer windings remain winding 2 and element 7 the magnetic field.

due to the flow of eddy currents in the element 7 will be opposed tothemagnetic field resulting from current flow in the winding 2, andconsequently the effective inductance of the winding 2 will be decreasedby adjusting the element 7 relatively to the winding. 2. The couplingtherebe-tween can be varied to control the amplitude of the eddycurrents and hence the value of the inductance introduced into thesecondary circuit. In this manner the tuning of the circuit includingthe winding 2 may be accurately adjusted.

Fig. 2 shows a circuit arrangement particularly adapted forpoint-to-point radio communication in which the above describedtransformer may be advantageously employed as a coupling means. Thisparticular system is given by way of illustration onl and notas alimitation upon the uses to whic the transformer may be applied.Obviously, the transformer is of general application in circuitsinvolving the use of a high frequency coupling means.

The radio receiver shown in Fig. 2 is adapted to operate on the basis ofthe well-known successive detection system in which the incoming signalwaves are combined with other oscillations to produce an auxiliaryinter'-.

' mediate frequency signal modulated wave,

which is then detected to yield the signal current. The receiverincludes a rotatable loop antenna 8 adapted to be sharply tuned to theincoming signal Wave'by an adjustable con-' denser 9. The received highfrequency'wave's are amplified bythe amplifiers 10 and 11 and impressedupon the input circuit of the'deteotor 12. The devices 10, 11 and 12areintercoupled by transformers 13, the construc- Heterodyne oscillationsare impressed upon the input circuit of detector 12 from source 14coupled to the input circuit of the detector by transformer 15. Theoutput circuit of the detector 12 includes a coupling inductance 16shunted by an anti-resonantcircuit 17 which is of high impedance for theauxiliary intermediate frequency, but provides a low impedance path forother frequencies.

The resultant intermediate frequency wave is amplified by the amplifiers18 and 19, transmitted through the selective means 20, and detected bythe device 21. The selective means 20 may be either a tuned circuitresonant to the intermediate frequency or a filter ada ted to freelypass a frequency band inclu ing the intermediate'frequency wave whilesuppressing frequencies outside this band. The low frequency currentsresulting from the second stage of detection are supplied to theindicating device 22 which may be of any well-known design but is hereinshown as a telephone receiver.

A system embodying certain apparatus and certain specific details hasbeen described for the purpose of completely and clearly disclosing theprinciples of the invention. However, it is to be understood that thisinvention is not limited to the arrangement or specific featuresdisclosed but only by the scope of the attached claims.

What is claimed is:

1. A couplin means for high frequency apparatus whic comprisesinductively associated coils, a resistance control element and aninductance control element respectively included in the magnetic fieldsof said coils.

2. A coupling means for high frequency apparatus which comprisesinductively asso ciated coils, an ad'ustable resistance control elementand an adjustable inductance control element respectively included inthe magnetic fields of said coils.

3. A transformer for coupling high frequency apparatus which includes aresistance control element in the magnetic field of one of said windingsand an inductance control element in the magnetic field of the other ofsaid windings. 4 4. A transformer for coupling high frequency apparatuswhich includes an adjustable resistance control element in the magneticfield of one of said windings and an adjustable inductance controlelement in the magnetic field of the other of said windings.

5. A coupling means for high frequency apparatus comprising inductivelycoupled coils and a variable resistance control element imizlluded inthe magnetic field of one of said co s. V

6. A coupling. means for high frequency amplifiers comprisinginductively coupled coils and a control element comprising a spirallywound ribbon of high resistance material included in the magnetic fieldof one of said coils. p

7. A coupling means for high frequency amplifiers comprising inductivelycoupled coils and a spirally wound iron ribbon included in the magneticfield of one of said coils.

8. A coupling means for high frequency amplifiers comprising inductivelycoupled coils and a control element comprising a spirally wound ribbonof high resistance material included in the magnetic field of one ofsaid coils, and means for adjusting said control element relatively tosaid coil.

9. A tuned coupling means for high frequency apparatus comprisinginductively coupled coils, and a conductive element included in themagnetic field of only one of 20 secondary, and to a negligible extentin that 2 of the primary.

11. A transformer including inductively coupled coils one of which isincluded in a circuit tuned to a wave of definite frequency, and meansfor varying the tuning of said circuit comprising anadwstable'conductive element in the magnetic field of the coil includedin said circuit, and to a negligible extent in the field of the othercoil.

In witness whereof, I hereunto subscribe ll my name this 17th day ofAugust A. D., 1925.

RAYMOND A. HEISING.

